The researchers recreated air with freeway particulate matter under controlled laboratory conditions. They used brain cellsin vitroas well as live mice. The particulate matter measured up to 200 nanometers in width.

They found that neurons involved in learning and memory showed significant damage; the mouse brains showed signs of inflammation associated with premature aging and Alzheimer’s disease; and neurons from developing mice did not grow as well.

Live mice get slightly brain damaged from freeway air. Now I partly regret attending USC (the air was much worse toward downtown LA 15 years ago). Of course, humans may be more robust, but I doubt it.